1. Field of the Invention
This invention relates to a knee brace, and more particularly, to a knee brace having an improved pivotal joint, which pivotally joins a thigh fixing part and a shank fixing part together, to produce an effect on a corrective treatment according to user's knee troubles.
2. Description of the Related Art
Conventionally, two types of knee-joint corrective knee braces for a case of degenerative knee arthrosis have been available, such as a knee brace characterized by providing a belt in a dog-legged shape as viewed front ways to put the knees to zero-degree positions between valgus and varus by the action of a belt traction force, and a knee brace characterized by providing a shank fixing part having a plurality of straps to impact the shanks in a corrective direction for fixation in place by the action of a strap pressing force.
However, as a result of practical uses, the knee-joint corrective knee brace for the case of degenerative knee arthrosis has had a disadvantage of being incapable of sufficient correction of the knee joints with the belt traction force. In addition, use of the knee brace for tibia correction merely with the straps presents disadvantages of needing a complicated installing work or the like by reason that strap adjustment or the like takes much time because of the use of a large number of straps, and also having little effect of the straps on the tibia correction.
As disclosed in Japanese Patent Publication No. 6-139 and U.S. Pat. No. 3,093,269, knee braces respectively having improved pivotal parts have been recently developed in order to dissolve the above disadvantages. A brace device disclosed in the Japanese Patent Publication No. 6-139 is characterized by providing a hinge device having a guide groove in the shape of a laterally longer slot, wherein upper and lower braces are formed movably in a lateral direction along the guide groove to make a motion in imitation of user's knee flexion.
Inventions disclosed in the U.S. Pat. No. 3,093,269 all relate to a detachable knee brace having an effect of permitting a knee motion to a certain degree, while holding the knees in place surely before and after higher tibia osteotomy. This knee brace is also supposed to be an orthotic device that takes the place of a conventional cast for knee fixation. In the U.S. Pat. No. 3,093,269, there are disclosed three kinds of inventions, that is, the invention characterized by providing a support plate having a shape conformable to a partial circular projection of each of an inside support plate and an outside support plate so as to be put between the inside support plate having the partial circular projection and the outside support plate having the partial circular projection in contact therewith, wherein a bolt is provided sidably in a slot formed in the support plate to unite the inside and outside support plates as one body, and an arm and the support plate having the slot are connected together through a joint having an inclination angle to make an inclination controllable by changing the inclination angle of the joint to a desired angle; the invention characterized by providing a hinge device between outside support plates having circular projections, wherein the hinge device is placed opposite to a knee joint medial portion such that a pair of upper and lower arms is moved pivotally toward a knee lateral side; and the invention characterized by pivotally connecting the arms to upper and lower extending parts of the support plate having the slot to constitute a rotary joint. According to the inventions disclosed in the U.S. Pat. No. 3,093,269, only in a case of knee flexion, in other words, when no load is applied to the knee joints, the pair of upper and lower arms is moved pivotally toward the knee lateral side, so that the bolt is allowed to shift in a protrusive direction of the circular projection-shaped support plate within the slot provided in the above support plate to perform knee traction in vertically opposite directions by the same distance as an amount of movement of the bolt in a height direction of the above support plate. On the other hand, in a case of knee extension, in other words, when a load is applied to the knees in a standing posture, the bolt is allowed to shift downwards to an outside end within the slot to place the pair of upper and lower arms at an angle of approximately 180 degrees, so that an effect of the arms on femur and tibia traction is lost. For this reason, a clearance is produced between the femur and the tibia by the action of the traction force of the arms to alleviate a pain in the knees at the time of knee flexion. On the other hand, since the traction force of the arms is lost at the time of knee extension, the application of the load to the knees occurs to bring a femur surface into contact with a tibia surface without leaving the clearance therebetween. As a result, the user feels the pain in one's knees.
Since the invention disclosed in the Japanese Patent Publication No. 6-139 as described above has the laterally longer slot, the upper and lower braces fixedly installed to the thigh and the shank using the straps are pivotally moved while making a movement by a distance corresponding to the lateral length of the slot. In this case, since neither the slot nor an axis has a portion having an anchoring function, the braces are allowed to move freely, so that the pivotal movement of each brace with a specific position as a center is made impossible. For this reason, the pivotal part in each brace is not stabilized in some cases, resulting in problems of having little effect on a corrective treatment based on traction suitable to a genu varum and a genu valgum and control of a tibia position for a case of ligament disease, for instance, although a degree of freedom of the knee motion is increased.
According to the inventions as disclosed in the U.S. Pat. No. 3,093,269, when the pivotal movement of the arms toward the knee lateral side occurs, the bolt is allowed to slide within the slot formed in the circular projection-shaped support plate to perform the knee traction by the same distance as the amount of movement of the bolt in the height direction of the above support plate so as to produce the clearance in the knee joints only at the time of knee flexion that needs no application of load to the knees, in other words, does not cause pain to the knee joints so much. However, at the time of knee extension that causes pain to the knee joints most severely because of the application of load to the knees, the clearance in the knee joints is lost again to bring the femur surface into contact with the tibia surface. Thus, the knee brace according to the above inventions has no effect of the traction force in the standing posture on valgus rotation at all, and as a result, brings about a situation that the user in the case of degenerative knee arthrosis becomes tired of having the knee braces on for a long period of time, by reason that any pain is not alleviated even though the user makes repeatedly flexion and extension, that is, walks with the knee braces on.